Box jellyfish envenomations account for myriad clinically significant sequelae, including debilitating sting-site pain and Irukandji syndrome, as well as in rare instances acute cardiovascular collapse and death, among residents and visitors to the U.S. coastal areas of Hawaii, Guam, Saipan, Florida, U.S. Virgin Islands and Puerto Rico. Cubozoan stings are also an increasing public health threat worldwide in tropical and subtropical areas of Australia, Indonesia, Thailand, Caribbean basin, Mediterranean Sea and Indian Ocean. Thus, there is an urgent need to better understand the pathogenesis of Irukandji syndrome, a potentially life-threatening sequelae with multi-systems symptoms and signs, suggestive of ?cytokine storm? and ?catecholamine surge?. Our long-term goal is to develop rapid diagnostics and effective treatments for the full spectrum of cubozoan envenomations. For the proposed research, our primary objective is to clarify the role of venom porins in the pathogenesis of Irukandji syndrome, by employing previously established in vitro and in vivo model systems. Our central hypothesis is that the cubozoan pore-forming proteins, or porins, induce a domino-type cascade of time-dependent pathophysiological effects on platelets, erythrocytes and peripheral blood mononuclear cells, including an initial dose-dependent release of biogenic amines and stored cytokines, which in turn causes a secondary induction of cytokine release from nave leucocytes, as well as endothelial cells, that comprises Irukandji syndrome. A venom biochemist and an animal model expert will achieve the following specific aims. Aim 1. Compare the in vitro dose- and time-dependent effects of cubozoan whole venom and purified porin on human peripheral blood monocytes and platelets. Aim 2. Compare the in vivo dose-dependent effects of cubozoan whole venom and purified porin in piglets. Whole blood cell-based assays and a piglet animal model will be used to determine whether cubozoan porins cause specific systemic inflammatory effects and to track sequential physiological and biochemical responses in time-course experiments. Preliminary studies demonstrate that a central aspect of the pathogenesis of life- threatening jellyfish envenomation and Irukandji syndrome involves immune cell responses to cubozoan venom. Thus, this exploratory research project addresses a critical unmet need to better understand the pathophysiological role of cubozoan porin in order to develop rapid diagnostics and effective treatments.